Radicalisation on social networks: the role of cognitive bias

Ghent University and LMU Munich present the first results of an international research on extremist communication on social networks.


In Europe, even in times of a pandemic, extremism remains a serious threat. The attack on the 25th of September, close to the former premises of “Charlie Hebdo”, has proved this once again.

To recruit and enthuse people for their cause, extremists are very active on social networks. According to a European survey (2018), 77% of adolescents have already been confronted with invocations to violent behaviour online. In November 2019, European security (Europol) removed more than 26,000 posts related to the Islamic state from social networks. However, this is only the tip of an iceberg that masks the propaganda practices of undercover actors: many extremists advocate violence without officially joining a terrorist organisation. They disseminate violent propaganda amidst mundane, neutral messages, which makes them potentially effective in attracting people who are in the process of radicalisation. At the same time, this tactic makes it difficult for official regulators to spot and delete extremist messages.

“Us against them”

Prof. Catherine Bouko is a researcher and specialist in discourse analysis at Ghent University. As part of the European project PRECOBIAS (*), her team has examined 3,000 Facebook and Instagram posts from extremist Salafists.

The analysis showed that 7 to 24% of the posts in each profile contained an opposition of Salafists against other groups (non-believers, Westerners, etc.). This opposition – “us against them” – is a first gateway to polarisation and, consequently, to radicalisation.

3 key elements in extremist Salafist discourse

Similar to propaganda of self-proclaimed “Islamic state”, this opposition to “enemy” groups is based on several elements.

  • The intensification of a crisis. Examples: persecution of Muslims then and now, criticism of international politics and the conditions of Muslim prisoners, etc.
  • The creation of a collective identity by turning prisoners and terrorists into heroes and sources of inspiration.
  • The impossibility of any relationship and the use of violence as a solution to the crisis. The use of violence is sometimes explicitly mentioned (in less than 1% of the posts), but in most cases it is implicit. This makes it possible to circumvent Facebook and Instagram’s community standards and avoid removal of the posts.

These propaganda techniques are not the prerogative of extremist Salafists. Similar techniques have been identified in the analysis of 500 right-wing extremist posts.

Mechanisms related to extremist content

So-called cognitive biases play a role in extremist narratives and in the potential effectiveness of extremist content. In the following, we present a short practical introduction of cognitive biases:

  • Confirmation bias explains the tendency to search for, favour, and interpret information in a way that it affirms our existing beliefs and opinions. People display this bias when they gather or remember information selectively, or when they interpret it in a biased way.
  • negativity bias explains why negative information stands out to us in a more distinct way and affects us more. This is for instance reflected in the way we process comments about our work. One negative comment can impact our mood much more than 10 positive remarks.
  • Hostile media bias refers to the tendency of individuals who have a strong pre-existing attitude on a certain issue to perceive media coverage as biased against their own views and in favour of the antagonists’ point of view.

The power of cognitive biases

By using the “us against them” narrative, extremists can activate so-called cognitive biases. These biases are not “brain bugs” and have nothing to do with intelligence. They are natural mechanisms of thought that cause us to deviate from rationality and critical judgement. They are potentially powerful levers for disinformation, polarisation and radicalisation. PRECOBIAS researchers have therefore analysed extremist propaganda from the perspective of cognitive biases, with regard to their effects and content characteristics.

Legitimising violence

Prof. Diana Rieger and Dr. Brigitte Naderer,  from the Ludwig-Maximilians-University in Munich (LMU), conducted psychological experiments as part of the PRECOBIAS project. They found that following the ingroup-outgroup bias, which means holding beliefs of one’s ingroup being superior to an outgroup, positively relates to higher levels of extremist attitudes. In addition, violence narratives activated a just-world belief (another cognitive bias). This means that, when respondents were confronted with invocations of violence, their belief of the world as a just place increased, probably as a way to make sense of the presented violent claims. This can lead to a legitimation of violence and reinforce the process of radicalisation.

The results of the PRECOBIAS research indicate that cognitive biases can make people more likely to respond to extremist narratives. This relationship has not been examined in extant research – it’s a world’s first! The researchers have approached the problem of radicalization from the point of view of citizens and young people in particular who read radical content online.


Prof. Catherine Bouko, Prof. Diana Rieger and Dr. Brigitte Naderer are at your disposal for further information or interview requests.

Pieter Van Ostaeyen, a Belgian specialist of Jihadism at the Catholic University of Leuven who collaborated on this project, is also available for interviews.


The European project PRECOBIAS aims to strengthen digital resilience and critical thinking skills in adolescents and young adults. It focuses on the mental processes at play when young people are confronted with extremist discourse online. PRECOBIAS targets young people who are radicalised or at risk of radicalisation. The project is also aimed at teachers and social workers who work with these young people. For those professionals, PRECOBIAS offers a MOOC and educational resources about cognitive bias and radicalisation (Spring 2021). Universities and organisations from six countries (Belgium, Germany, Italy, Slovakia, Hungary, Poland) are collaborating in the context of PRECOBIAS.